package com.lark.sqlsession;

import com.lark.config.BoundSql;
import com.lark.pojo.Configuration;
import com.lark.pojo.MappedStatment;
import com.lark.utils.GenericTokenParser;
import com.lark.utils.ParameterMapping;
import com.lark.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor{

    @SuppressWarnings("unchecked")
    @Override
    public <E> List<E> query(Configuration configuration, MappedStatment mappedStatment, Object... params) throws Exception {
        // 1.注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2.获取sql： SELECT * FROM user WHERE id = #{id} and username = #{username}
        //  转换sql:   SELECT * FROM user WHERE id = ? and username = ? ，转换的过程中，还需要对#{}里面的值进行解析存储
        String sql = mappedStatment.getSql();
        BoundSql boundSql = getBoundSql(sql);

        // 3.获取预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //  4.设置参数
        String parameterType = mappedStatment.getParameterType();
        Class<?> parameterTypeClass = getClassType(parameterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(0);
            String content = parameterMapping.getContent();
            // 反射获取字段
            Field declaredField = parameterTypeClass.getDeclaredField(content);
            //  暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i + 1, o);

        }

        // 5. 执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatment.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        ArrayList<Object> objects = new ArrayList<>();
        while(resultSet.next()) {
            Object o = resultTypeClass.getDeclaredConstructor().newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                // 字段名
                String columnName = metaData.getColumnName(i);
                Object value = resultSet.getObject(columnName);
                // 使用内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);

            }
            objects.add(o);

        }
        return (List<E>) objects;
    }

    private Class<?> getClassType(String parameterType) throws ClassNotFoundException {
        if (parameterType!= null) {
            Class<?> aClass = Class.forName(parameterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作：1.将#{}使用？进行代替，2.解析出#{}里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql,parameterMappings);
        return boundSql;
    }
}
